Endoscopic ultrasound-guided tissue acquisition allows a reliable proliferation assessment of small (≤20 mm) pancreatic neuroendocrine tumors.

Aim: Evidence regarding the reliability of endoscopic ultrasound-guided tissue acquisition (EUS-TA) for assessing histological proliferation and WHO grading of small (≤20 mm) pancreatic neuroendocrine tumors (PanNETs) is limited.

Methods: In this multicenter retrospective study, we analyzed data from 122 patients with small PanNETs who underwent EUS-TA followed by surgical resection between 2006 and 2022. We compared the histopathological proliferation assessment and WHO grading between preoperative EUS-TA and surgical definitive specimens.

Results: Among the 122 patients with small PanNETs (80% with surgical definitive WHO grade G1 and 20% with G2), EUS-TA histology identified neuroendocrine tumors in 101 (83%) patients and provided WHO grading in 85 (70%) patients. Histopathological WHO grading for EUS-TA was concordant with surgical definitive grading in 86% (73/85) of cases, overstaged in 4% (3/85), and understaged in 11% (9/85). Moderate, severe, and fatal adverse events associated with EUS-TA, as classified by the lexicon, were not reported in this cohort.

Conclusion: EUS-TA is a reliable method for assessing histopathological proliferation and WHO grading of small PanNETs. However, grading discordance may occur, and a risk-benefit evaluation on a per-patient basis is recommended.